Beach Dune Erosion
Uploaded by Gotskillz on Feb 02, 2005
Vegetated sand ridges called dunes, built up by dry beach sand blown inland and trapped by plants and other obstructions, back most beaches. As sand accumulates, the dunes become higher and wider.
Plants play a vital role in this process, acting as a windbreak and trapping the deposited sand particles. A characteristic of these plants is their ability to grow up through the sand and continually produce new stems and roots as more sand is trapped and the dune grows.
Stable sand dunes play an important part in protecting the coastline. They act as a buffer against wave damage during storms, protecting the land behind from salt-water intrusion. This sand barrier allows the development of more complex plant communities in areas protected from salt-water inundation, sea spray and strong winds. The dunes also act as a reservoir of sand, to replenish and maintain the beach at times of erosion.
Frontal sand dunes are vulnerable. The vegetation can be destroyed by natural causes such as storms, cyclones, droughts or fire, or by human interference such as clearing, grazing, vehicles or excessive foot traffic. If the vegetation cover is damaged strong winds may cause 'blowouts' or gaps in the dune ridge. Unless repaired, these increase in size, the whole dune system sometimes-migrating inland covering everything in its path. Meanwhile, with a diminished reservoir of sand, erosion of the beach may lead to coastal recession.
To avoid this, protecting the vegetation is vital. The beach, between high and low tides, is hard-wearing but the sensitive dunes, which we cross to reach it, must be protected also. For this reason damaged and sensitive dunes might need to be fenced and access tracks for vehicles and people provided.
Processes such as waves, near shore currents and tides continually modify shorelines. The ability of beaches to maintain themselves is achieved through these natural forces. The natural process of beach renourishment, sometimes called "dynamic equilibrium", is how the beach responds to weather. When waves are high during storms or when hurricanes hit the shore, sand is carried from the beach and deposited on the ocean floor. This makes the ocean bottom flatter and makes waves break further from shore and smaller. During subtle weather or erosion, smaller waves slowly shift the sand back to the shore and replenish the beach.
When people build homes or resorts on beaches, the buildings interrupt this natural process because the sand that is usually taken...